We plan to continue our studies on the basic principles of the protein- nucleic acid interactions that underlie the regulation of gene expression. During the next reporting period we plan to continue our biophysical investigations of transcription in the E.coli system, focusing on: (i) regulation of the overall transcription cycle from the point-of-view of the structure and function of the initiation, elongation, and termination transcription complexes; (ii) the molecular bases of the control of the elongation-termination (and elongation- editing) decision at each DNA template position; (iii) the detailed steps involved in the addition of a single nucleotide residue to the 3'OH-end of the nascent RNA chain of a "stalled" elongation complex, including the molecular bases and thermodynamic and kinetic consequences of polymerase "pausing", translocation of the polymerase (forward and backward) along the template (and the nascent transcript), nucleotide addition and editing by GreA- and GreB-induced cleavage of the 3'-end of the nascent chain, etc.; (iv) the role of termination and antitermination transcription factors in controlling termination efficiencies at intrinsic and rho-dependent terminators (focusing, in particular, on the N-protein-dependent antitermination systems of phage gamma); and (v) further studies if the mechanisms whereby transcription factor rho of E. coli works to bring about termination at rho-dependent terminators. As before, we will attempt both to examine specific physiologically-important protein-nucleic acid complexes involved in gene expression and to elucidate some of the general principales that direct and regulate the function of these systems.